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Basic Communications

Basic Communications. Overview of communication technology. Communications. Electronically exchanging data or information. Voice interactive communication Data large volume batch transmissions Image encoded graphics Video streaming media. Telecommunications History. Pre 1984

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Basic Communications

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  1. Basic Communications Overview of communication technology.

  2. Communications Electronically exchanging data or information. • Voice interactive communication • Data large volume batch transmissions • Image encoded graphics • Video streaming media

  3. Telecommunications History • Pre 1984 Local and long distance monopoly • 1984 AT&T settlement Intense long distance competition • 1996 Telecommunications Act Local access competition

  4. Analog Analog Digital Digital Modem Digital Network Network Standard Telephone System Switch Switch Switch

  5. Telephone Changes • Rapidly decreasing long distance rates • Value added telephone services • Cellular access • Flat rate long distance? • Data and voice convergence.

  6. Issue: Access • Dedicated lines • Standard voice • Integrated Services Digital Network • Digital Subscriber Lines • Cable Modem • Wireless

  7. Voice Delay Sensitive Constant bit rate Not error sensitive Growth stable (video ??) Data Delay insensitive Variable bit rate Error sensitive Demand growing Voice vs. Data

  8. NIC LAN Switch Campus or Metropolitan Area Router Public TELCO WAN POP Data Networks

  9. Packet Structure Header(s) Data Payload Trailer

  10. LAN Operating Protocols (layer 2) • Ethernet open standard, cheap, most common • Token Ring IBM proprietary, high quality, expensive • Others

  11. Network Interface Cards • Build, send out and accept frames • Usually a daughter board on PC • Must match LAN and CPU • Require drivers to operate

  12. Network Interface Cards (NIC)

  13. EthernetCarrier Sense Multiple Access/Collision Detection Header Trailer Body Listen before transmit Contention access Retransmit on collision

  14. Network Routing Protocols for internetworking.

  15. Two major types • Packet switching (or datagram) • Usually layers 3 and 4 • Circuit switching • Usually layers 1 and/or 2

  16. Packet switching or Datagram Protocols • Best effort • Frames take individual routes • Packet assembly devices needed • Error Control • Traffic Management • Buffering • Discard

  17. Datagram Logic (IP) Packet n Packet 2 Packet 1 1 3 2 3 1 2 3 1 PAD 2

  18. IP • Best Effort • Addressing • Variable packet lengths (1500 bytes or less) • IPv4 vs IPv6 • Frame and Header

  19. Transmission Control Protocol Connection oriented Assures that packets arrive in order and that they are correct. User Datagram Protocol Connectionless Sends packets out without confirming that they arrive TCP and UDP

  20. Ethernet/TCP/IP Header Structure

  21. Circuit Protocols • All packets take the same route • No packet assembly device to reorder packets • Normally layer 2 connection • May be permanent or switched • Allow guaranteed service quality levels • May be used to carry datagram protocols

  22. Source Destination Setup Message & ACK’s Teardown Circuit Logic

  23. 1 Inter-networking 3 2 1 2 3

  24. Technologies Common WAN technologies.

  25. ISDN Circuit Switched Data and Voice Service

  26. Digital Subscriber Lines DSL uses packet switching technology that operates independent of the voice telephone system, allowing the telephone companies to provide the service and not lock up circuits for long calls.

  27. WAN Costs • Circuit Charges • Committed Bandwidth • Peak Bandwidth • Discard Priority • Latency

  28. Representative Prices per MB of traffic (Qwest, Dec. 98) • Frame Relay Non-discard eligible 4 cents Discard eligible 3 cents • ATM Constant bit rate 2 cents Variable bit rate (real-time) 1.2 cents Variable bit rate (non real-time) .75 cents Available bit rate .55 cents Unspecified bit rate .4 cents

  29. Representative Prices per port (Qwest, Dec. 98) • 56 Kb Frame Relay $190 • T-1 Frame Relay $1,595 • T-3 Frame Relay $3,190

  30. Client/Server Architecture An architecture in which the client (personal computer or workstation) is the requesting machine and the server is the supplying machine, both of which are connected via a network.

  31. Client/Server Architectures FAT CLIENT FAT SERVER SERVER PROCESSING CLIENT PROCESSING CENTRALIZED STAND-ALONE

  32. Client/Server • Scalability • Interoperability • User buy-in • Increased cost • Multi-tier

  33. One Tier System

  34. Two Tier Client/Server

  35. Three Tier Client/Server

  36. Application Issues • Interoperability (e.g. ODBC) • OS support • Multi-threaded or single threaded • Network impact (e.g. chattiness) • QoS demands • Delivery: centralized, clien/server, web

  37. Application Management • Standards • Supported • Accepted • Prohibited • Version Control and Distribution • License Management • Virus detection and inoculation

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